support non-standard rvm install prefixes

themes/bira.zsh-theme

@@ -3,7 +3,7 @@ local return_code="%(?..%{$fg[red]%}%? ↵%{$reset_color%})"
 
 local user_host='%{$terminfo[bold]$fg[green]%}%n@%m%{$reset_color%}'
 local current_dir='%{$terminfo[bold]$fg[blue]%} %~%{$reset_color%}'
-local rvm_ruby='%{$fg[red]%}‹$(~/.rvm/bin/rvm-prompt i v g)›%{$reset_color%}'
+local rvm_ruby='%{$fg[red]%}‹$(rvm-prompt i v g)›%{$reset_color%}'
 local git_branch='$(git_prompt_info)%{$reset_color%}'
 
 PROMPT="╭─${user_host} ${current_dir} ${rvm_ruby} ${git_branch}